In his first television interview as Homeland Security secretary, retired four-star Marine Gen. John F. Kelly told Fox News he wants the U.S.-Mexico border wall finished in two years – setting an ambitious schedule for the project ordered last week by President Trump.

“The wall will be built where it’s needed first, and then it will be filled in. That’s the way I look at it,” Kelly said. “I really hope to have it done within the next two years.”

Fox News traveled with Kelly in McAllen, Texas, on Wednesday where he saw first-hand the challenges for Border Patrol agents. The Rio Grande Valley, known as the “RGV sector,” is among the busiest. On any given day, Border Patrol agents pick up at least 600 people who have crossed the Mexican border, entering the U.S. illegally.

Those personnel, he explained, are all part of the broader plan for securing the border.

“Any discussion about the protection of our southwest border involves discussion of physical barriers but also of technological sensors, things like that,” he said. “But it’s a layered approach, and it’s got to be backed up by great men and women who are going to make sure that the wall is intact.”